The present invention relates in general to signal transmission, reception, and processing and more particularly to a method and apparatus for modulating a signal.
The challenges for any high speed communications, whether it be over wireless, copper wire, fiber optic, or other means, is to provide sufficient bandwidth to meet user demand. With the advent of Internet access and video on demand, the demand for higher bandwidth has exponentially increased. Users want bandwidth for Internet connections, video applications, simultaneous Internet and telephony capability, and enhanced telephony data processing quality and feature sets. However, service providers want to utilize the existing infrastructure as much as possible but avoid having heavy data users from congesting the telephony network.
In order to use the existing wired, wireless, or fiber optic infrastructure to deliver high bandwidth to subscribers, certain modulation techniques have been implemented in order to provide a transmission capability. These modulation techniques include Amplitude Shift Keying, Frequency Shift Keying, Phase Shift Keying, Quadrature Amplitude Modulation, Carrierless Amplitude Phase Modulation, Frequency/Time/Code Division Multiple Access Discrete Multi-Tone, and various combinations of each technique. These modulation techniques require the use of mixing the baseband digital signal with a carrier signal. This mixing process requires further filtering to select the desired signal.
Existing modulation techniques also suffer from an intersymbol interference phenomenon. With any practical channel, the inevitable filtering effect will cause a spreading or smearing of individual data symbols through the channel. For consecutive symbols, this spreading causes part of the symbol energy to overlap with neighboring symbols, resulting in intersymbol interference. Moreover, filtering in a transmitter or receiver may also introduce intersymbol interference degradation. Intersymbol interference can significantly degrade the ability of a receiver to differentiate a current symbol from diffused energy of adjacent symbols.
As can be seen, conventional modulation techniques suffer from low symbol state representation capabilities that limit the bandwidth of a digital communication system. Therefore, it is desirable to modulate a signal for transmission that avoids the problems inherent in conventional modulation techniques.
From the foregoing, it may be appreciated by those skilled in the art that a need has arisen for an improved modulation technique that reduces noise in signal transmission and reception and increases bandwidth capability in a communication system. In accordance with the present invention, a method and apparatus for modulating a signal are provided that substantially eliminate or reduce disadvantages and problems associated with conventional modulation techniques.
According to an embodiment of the present invention, there is provided a method for modulating a signal that includes generating a sinusoidal wave signal and encoding each half wave cycle of the sinusoidal wave signal with digital data.
The present invention provides various technical advantages over conventional modulation techniques. For example, one technical advantage is to avoid using a mixing process to perform modulation and avoid Manchester encoding for return to zero coding that reduces the available bandwidth. Another technical advantage is to provide full duplex bidirectional communications on the same modulated sinusoidal wave signal. Yet another technical advantage is to use the modulated sinusoidal wave signal to carry the encoded digital data as well as to provide a reference oscillator clock for synchronization between communication nodes. Still another technical advantage is to provide multiple symbol states per half wave or quarter wave sinusoidal wave signal. Other technical advantages may be readily apparent to those skilled in the art from the following figures, description, and claims.